This invention relates in general to the field of devices and apparatus for keeping food warm and more particularly to devices and apparatus for keeping pizzas and other food items hot until delivered to the consumer.
The prior art encompasses a wide variety of devices and apparatus for reducing the rate at which pizzas cool, allowing them to be delivered before they have cooled to the ambient temperature. Such products are generally inadequate, since the consumer wants pizza to be hot when delivered. There are also devices for keeping pizzas hot until delivered to the consumer, generally containing a phase change material which releases its latent heat of fusion to maintain the temperature of the pizzas. These devices work well but must be charged to their usable temperatures by absorbing their latent heat of fusion. This is done in a variety of ways: by heating in an oven, by heating in a microwave oven and by heating caused by contact with a resistance heating element. However, all of these methods require considerable time in which to charge the pizza warmer and also require someone to attend to and monitor any such charging of a pizza warmer. Any additional time required to deliver pizzas is a major disadvantage since staying competitive requires the shortest delivery times. Likewise, the additional time required by someone to charge the pizza warmers takes personnel away from being able to take orders and make pizzas which adds cost and reduces efficiency.
The pizza warmer and oven system of the present invention enables a charged pizza warmer to be ready and available for use in delivering hot pizzas to the consumer without adding to the delivery time or requiring more than minimal effort or attention. The pizza warmer of the invention is generally circular in shape, one embodiment having flats on opposing lateral sides, and contains a phase change material, hereinafter referred to as (xe2x80x9cPCMxe2x80x9d) which, when charged, gives up its latent heat of fusion to keep the pizza hot during delivery. The pizza warmers are charged in an oven equipped to hold and charge a plurality of pizza warmers, each in a separate chamber or slot. Heating elements in each slot charge the pizza warmer and the insulated oven maintains the pizza warmers at their preferred useful temperature. When a pizza must be delivered, an already charged pizza warmer can be removed from the oven, a hot pizza can be placed on the warmer and they can both be placed in an insulated box for delivery to the consumer. During delivery the warmer releases some of its latent heat of fusion, keeping the pizza hot for delivery.
Other advantages and attributes of this invention will be readily discernable upon a reading of the text hereinafter.
An object of this invention is to provide a pizza warmer and oven system for charging a plurality of pizza warmers and maintaining their preferred charged temperature in readiness for use to keep pizza hot during delivery to a consumer.
An additional object of this invention is to provide a pizza warmer and oven system having a plurality of pizza warmers which contain a phase change material.
An additional object of this invention is to provide disk shaped pizza warmers.
An additional object of this invention is to provide disk shaped pizza warmers having opposing flats parallel to a longitudinal axis through a handle.
An additional object of this invention is to provide a pizza warmer having a handle near its perimeter.
An additional object of this invention is to provide a pizza warmer having a handle for grasping which stays cool to the touch, allowing ease of handling of charged pizza warmers.
An additional object of this invention is to provide an oven having a plurality of pizza warmer charging slots, each of which can charge a pizza warmer to its preferred charged temperature.
An additional object of this invention is to provide an oven having charging slots that will accept a pizza warmer with opposing flats only if properly aligned.
An additional object of this invention is to provide an oven having heating elements affixed to the top and bottom shelves adjacent each charging slot.
An additional object of this invention is to provide an oven in which pizza warmers inserted into the charging slots are maintained in close proximity to the slot""s top and bottom shelves for heating by the heating elements.
An additional object of this invention is to provide an oven in which the top shelves are biased downward, maintaining the heating elements in close proximity to the top and bottom surfaces of installed pizza warmers.
An additional object of this invention is to provide an oven with charging slot top shelves which can be raised to allow the easy removal and insertion of pizza warmers.
An additional object of this invention is to provide an oven in which the charging slot""s top shelves are gravitationally biased downward but can individually be lifted by the insertion of a pizza warmer.
An additional object of this invention is to provide an oven in which all the charging slot""s top shelves can be lifted in unison.
An additional object of this invention is to provide an oven in which a cam plate can be rotated by a lever.
An additional object of this invention is to provide an oven in which a lift plate can be raised by cams on the cam plate engaging cams on the lift plate when the cam plate is rotated by the lever.
An additional object of this invention is to provide an oven in which the lift plate is affixed to the top shelves, by means of lift rails, allowing the top shelves to be raised and lowered with the lift plate.
An additional object of this invention is to provide an oven having detent balls in the cams to maintain the position of the cams when in the raised position until the lever is used to move the cams.
An additional object of this invention is to provide an oven in which the insertion of a pizza warmer in a charging slot completes the lighting circuit through the warmer.
An additional object of this invention is to provide an oven in which switches enable the heating elements to each charging slot when a pizza warmer is installed therein.
An additional object of this invention is to provide an oven in which each shelf has a thermostat for maintaining the pizza warmers at their preferred charged temperature.
An additional object of this invention is to provide an oven in which indicator lights indicate whether each pizza warmer has obtained its preferred charged temperature.
An additional object of this invention is to provide an oven in which indicator lights indicate whether each pizza warmer is being charged, or has obtained its preferred charged temperature.
An additional object of this invention is to provide an oven in which the top shelves are held against an installed pizza warmer by gravity.
An additional object of this invention is to provide an oven in which the charging slot""s bottom surfaces can be lowered for release or insertion of warmers and lifted into close proximity with the warmer for charging.
A further object of this invention is to provide an oven which allows the handles of charged pizza warmers to remain unheated, enabling the charged pizza warmers to be safely grasped.
These objects, and other objects expressed or implied in this document, are accomplished by disk shaped pizza warmers containing a phase change material such as fiberboard impregnated with a phase change material, an individual warmer or a plurality of the warmers can be charged to their preferred useful temperature by charging them in an oven having a plurality of charging slots to heat the warmers. The slots are defined by upper and lower shelves, each containing a heating element positioned to be in close proximity with the warmers in the charging slots. The upper shelves are gravitationally biased downward but can easily be raised by insertion of a warmer. The gravitational biasing of the upper shelves keeps them against the upper surface of the warmers. The warmers have a handle defined near a perimeter and opposing flats parallel to a longitudinal axis centered through the handle. Guides along the sides of the slots allow the warmers to be inserted only when the warmers"" flats are aligned parallel to the sides of the slots. Inserting a warmer into a charging slot allows spring contacts in the sides of the slot to make electrical connection with the warmer""s thermal switch circuit contacts in the flats. When the warmer has been heated to its desired operating temperature, the thermal switch closes, causing the slot""s charging light to indicate that the warmer has been charged. A thermostat for each charging slot allows the heating elements to keep the warmer at its preferred temperature. The warmer""s handle remains outside of the charging slot when the warmer is installed, allowing a charged warmer to be safely grasped by the handle when needed for use. When needed, a warmer can be removed from the oven, inserted in an insulated container with a pizza to keep the pizza hot during delivery to the consumer.
These objects, and other objects expressed or implied in this document, are also accomplished in an additional embodiment by disk shaped pizza warmers containing a phase change material such as fiberboard impregnated with a phase change material, a plurality of the warmers can be charged to their preferred useful temperature by charging them in an oven having a plurality of charging slots to heat the warmers. The slots are defined by upper and lower shelves, each containing a heating element positioned to be in close proximity with the warmers in the charging slots. The upper shelves can be raised for ease of removal or insertion of the warmers. The upper shelves are lifted by lift rails affixed to a lift plate which is raised by cams which engage when a the movement of a lever causes a cam plate to rotate, thereby engaging the cams. Inserting a warmer into a charging slot trips a switch which starts a timing circuit and applies power to the heating elements. The timing circuit turns on indicator lights to indicate the charging of the warmers. When the preset charging time has expired the charging indicator lights are turned off and the charged indicator lights are lit. A thermostat for each charging slot allows the heating elements to keep the warmer at its preferred temperature. The warmers have a handle defined near a perimeter which remain outside of the charging slot when the warmer is installed, allowing a charged warmer to be safely grasped by the handle when needed for use. When needed, a warmer can be removed from the oven, inserted in an insulated container with a pizza to keep the pizza hot during delivery to the consumer.